$\dfrac{2}{5} + \dfrac{1}{4} = {?}$
Solution: ${\dfrac{2}{5}}$ ${\dfrac{1}{4}}$ $+$ ${\dfrac{2 \times 4}{5 \times 4}}$ ${\dfrac{1 \times 5}{4 \times 5}}$ $+$ ${\dfrac{8}{20}}$ ${\dfrac{5}{20}}$ $+$ $ = \dfrac{{8} + {5}}{20} $ $ = \dfrac{13}{20}$